ALDIBBIAT, Nawras Mohamed (2001). Optical wireless communication systems employing dual header pulse interval modulation (DH-PIM). Doctoral, Sheffield Hallam University. [Thesis]
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10694116.pdf - Accepted Version
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Abstract
Indoor optical wireless communication systems have been shown to be viable
alternatives to radio systems for indoor networks because optical wireless systems
offer a huge unlicensed bandwidth, high data rates, secure connectivity, immunity to
electromagnetic interference and prevention from multipath fading. However, optical
wireless systems are subject to multipath distortion and are governed by eye safety
standards. Therefore, a modulation scheme is required that is capable of providing high
speed and good immunity to multipath dispersion on indoor optical channels.
In this thesis, a critical review of optical wireless systems and suitable modulation
schemes has been presented. A new modulation scheme called dual header pulse
interval modulation (DH-PTh1) is presented. A comprehensive theoretical analysis
supported by computer simulations has been carried out to study characteristics of
DH-PTh1. Novel expressions for the DH-PTh1 pulse train, symbol length, bandwidth
requirement, packet transmission rate, transmission capacity, Fourier transform, power
spectral density, slot and packet error rates and power requirement and penalty due to
multipath propagation have been presented.
Results from the analyses have been compared with OaK, PPM and DPTh1 modulation
schemes. It has been shown that DH-PTh1 is a viable alternative scheme for indoor
optical wireless communications, due to its built-in symbol synchronisation and
relatively easy slot synchronisation. Compared with PPM and DPIM, DH-PIM offers
shorter symbol lengths, improved transmission rates, increased transmission capacity,
improved bandwidth requirement and better immunity to multipath dispersion when
the dispersion is high. However these features are at the expense of a slightly higher
optical power requirement and increased probability of error. The proposed scheme is
suitable for applications where there is a need for high throughput.
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